This invention relates to support structures such as bridges, piers, docks, load bearing decking applications, such as hulls and decks of barges, and load bearing walls. More particularly, this invention relates to a modular composite load bearing support structure including a polymer matrix composite modular structural section for use in constructing bridges and other load bearing structures and components.
Space spanning structures such as bridges, docks, piers, load bearing walls, hulls, and decks which have provided a span across bodies of water or separations of land and water and/or open voids have long been made of materials such as concrete, steel or wood. Concrete has been used in building bridges, and other structures including the columns, decks, and beams which support these structures.
Such concrete structures are typically constructed with the concrete poured in situ as well as using some preformed components precast into structural components, such as supports, and transported to the site of the construction.
Constructing such concrete structures in situ requires hauling building materials and heavy equipment and pouring and casting the components on site. This process of construction involves a long construction time and is generally costly, time consuming, subject to delay due to weather and environmental conditions, and disruptive to existing traffic patterns when constructing a bridge on an existing roadway.
On the other hand, pre-cast concrete structural components are extremely heavy and bulky and are typically costly and difficult to transport to the site of construction due in part to their bulkiness and heavy weight. Although construction time is shortened compared to construction with concrete poured in situ, extensive construction time with resulting delays is still a factor. Bridge construction with such precast forms is particularly difficult, if not impossible, in remote or difficult terrain such as mountains or jungle areas in which numerous bridges are constructed.
In addition to construction and shipping difficulties with concrete bridge structures, the low tensile strength of concrete can result in failures in concrete bridge structures, particularly in the surface of bridge components. Reinforcement is often required in such concrete structures when subjected to large loads such as in highway bridges. Steel and other materials have been used to reinforce concrete structures. If not properly installed, such reinforcements cause cracking and failure in the reinforced concrete, thereby weakening the entire structure. Further, the inherent hollow spaces which exist in concrete are highly subject to environmental degradation. Also, poor workmanship often contributes to the rate of deterioration.
In addition to concrete, steel also has been widely used by itself as a building material for structural components in structures such as bridges, barge decks, vessel hulls, and load bearing walls. While having certain desirable strength properties, steel is quite heavy and costly to ship and can share construction difficulties with concrete as described.
Steel and concrete are also susceptible to corrosive elements, such as water, salt water and agents present in the environment such as acid rain, road salts, chemicals, oxygen and the like. Environmental exposure of concrete structures leads to pitting and spalling in concrete and thereby results in severe cracking and a significant decrease in strength in the concrete structure. Steel is likewise susceptible to corrosion, such as rust, by chemical attack. The rusting of steel weakens the steel, transferring tensile load to the concrete, thereby cracking the structure. The rusting of steel in stand alone applications requires ongoing maintenance, and after a period of time corrosion can result in failure of the structure. The planned life of steel structures is likewise reduced by rust.
The susceptibility to environmental attack of steel requires costly and frequent maintenance and preventative measures such as painting and surface treatments. In completed structures, such painting and surface treatment is often dangerous and time consuming, as workers are forced to treat the steel components in situ while exposed to dangerous conditions such as road traffic, wind, rain, lightning, sun and the like. The susceptibility of steel to environmental attack also requires the use of costly alloys in certain applications.
Wood has been another long-time building material for bridges and other structures. Wood, like concrete and steel, is also susceptible to environmental attack, especially rot from weather and termites. In such environments, wood encounters a drastic reduction in strength which compromises the integrity of the structure. Moreover, wood undergoes accelerated deterioration in structures in marine environments.
Along with environmental attack, deterioration and damage to bridges and other traffic and load bearing structures occurs as a result of heavy use. Traffic bearing structures encounter repeated heavy loads of moving vehicles, stresses from wind, earthquakes and the like which cause deterioration of the materials and structure.
For the reasons described above, the United States Department of Transportation xe2x80x9cBridge Inventoryxe2x80x9d reflects several hundred thousand structures, approximately forty percent of bridges in the United States, made from concrete, steel and wood are poorly maintained and in need of rehabilitation in the United States. The same is believed to be true for other nations.
The associated repairs for such structures are extremely costly and difficult to undertake. Steel, concrete and wood structures need welding, reinforcement and replacement. Decks and hulls of structures in marine environments rust, requiring constant maintenance and vigilance. In numerous instances, these necessary repairs are not feasible or economically justifiable and cannot be undertaken, and thereby require the replacement of the structure. Further, in developing areas where infrastructures are in need of development or improvement, those constructing bridges and other such structures utilizing concrete, steel and wood face unique difficulties. Difficulty and high cost has been associated with transporting materials to remote locations to construct bridges with concrete and steel. This process is more costly in marine environments where repairs require costly dry-docking or transport of materials. Also, the degree of labor and skill is very high using traditional building materials and methods.
Further, traditional construction methods have generally taken long time periods and required large equipment and massive labor costs. Thus, development and repair of infrastructures through the world has been hampered or even precluded due to the cost and difficulty of construction. Further, in areas where structures have been damaged due to deterioration or destroyed by natural disaster such as earthquake, hurricane, or tornado, repair can be disruptive to traffic or use of the bridge or structure or even delayed or prevented due to construction costs.
In addressing the limitations of existing concrete, wood and steel structures, some fiber reinforced polymer composite materials have been explored for use in constructing parts of bridges including foot traffic bridges, piers, and decks and hulls of some small vessels. Fiber reinforced polymers have been investigated for incorporation into foot bridges and some other structural uses such as houses, catwalks, and skyscraper towers. These composite materials have been utilized, in conjunction with, and as an alternative to, steel, wood or concrete due to their high strength, light weight and highly corrosion resistant properties. However, it is believed that construction of traffic bridges, marine decking systems, and other load bearing applications built with polymer matrix composite materials have not been widely implemented due to extremely high costs of materials and uncertain performance, including doubts about long term durability and maintenance.
As cost is significant in the bridge construction industry, such materials have not been considered feasible alternatives for many load bearing traffic bridge designs. For example, high performance composites made with relatively expensive carbon fibers have frequently been eliminated by cost considerations. These same cost considerations have inhibited the use of composite materials in decking and hull applications.
In investigating providing structural components made from fiber reinforced polymer composite materials, components structures from prior materials such as steel, concrete and wood have been investigated. Steel trusses and supports have utilized triangular shapes welded together. Providing triangular structural components with composite materials has presented problems of failure in the resin bonded nodes of the triangular shape. Therefore a modular structural composite component for structural supports is needed which overcomes this problem.
In view of the problems associated with bridges and other structures formed of steel, concrete, and wood described herein, there remains a need for a bridge or like support structure with the following characteristics: light-weight; low cost, pre-manufactured; constructed of structural modular components; easily shipped, constructed, and repaired without requiring extensive heavy machinery; and resistant to corrosion and environmental attack, even without surface treatment. There is also a need for a support structure which can provide the structural strength and stiffness for constructing a highway bridge or similar support structure.
In view of the foregoing, it is therefore an object of the present invention to provide a load bearing support structure suitable for a highway bridge structure or decking system in marine and other construction applications, constructed of modular structural sections formed of a lightweight, high performance, environmentally resistant material.
It is another object of the invention to provide a support structure such as a highway bridge structure which satisfies accepted design, performance, safety and durability criteria for traffic bearing bridges of various types.
It is another object of the present invention to provide such a support structure in the form of a traffic-bearing bridge in a variety of designs and sizes constructed of modular structural sections which can be constructed quickly, cost-effectively and with limited heavy machinery and labor.
It is also an object of the present invention to provide such a support structure, such as a bridge, constructed of components which can easily and cost-effectively be shipped to the site of construction as a complete kit.
It is likewise an object of the present invention to provide a support structure including a modular structural section which can be utilized to quickly repair or replace a damaged bridge, bridge section or like support structure.
It is another object of the present invention to provide a load bearing support structure including a modular structural section which can be used in decking, hull, and wall applications.
It is still another object of the invention to provide a support structure or bridge which requires minimal maintenance and upkeep with respect to surface treatment or painting.
These and other objects, advantages and features are satisfied by the present invention, which is directed to a polymer matrix composite modular load bearing support structure described herein for exemplary purposes in the form of a highway bridge. The support structure of the present invention includes a plurality of support members and at least one modular structural section positioned on and supported by the support members. The modular structural section is preferably formed of a polymer matrix composite.
The modular structural section includes at least one beam and a load bearing deck positioned above and supported by the beam. The at least one beam includes a pair of lateral flanges and a medial web between and extending below the flanges. In one embodiment, the flanges and the web have a predetermined shape which matably contacts surfaces of support means which also have a predetermined contoured shape. The flanges and web are positioned on and supported the contoured shaped support means. In a preferred embodiment, the lateral flanges and the web also preferably form a U-shaped cross-section having a generally flat floor in the medial portion.
In an alternative embodiment, the flat floor of the elongate support can be positioned on and supported by support means having a surface having a generally flat portion preferably a support member or abutment with a flat cap portion.
In a further alternative embodiment, the support means in the form of a support member or abutment can be provided having a surface having a horizontal cap surface perpendicular to a vertical wall surface forming an L-shape surface for supporting the beam and deck of the modular structural section. The beam is preferably positioned, in this embodiment with the flat floor positioned above the horizontal cap surface and the end edge of the web and flanges of the modular structural section positioned flush with the vertical wall surface.
In all of these embodiments, the polymer matrix composite support structure of the present invention can provide a support surface sufficient to support vehicular traffic and to conform to established design and performance criteria.
Alternatively, the modular structural section, including the load-bearing deck and beam, can be used in constructing other support structures including space-spanning support structures. Further, the load bearing deck can also be used as a stand alone decking, hull, or wall system which can be integrated into a marine or construction system. The load bearing decking system can be utilized in numerous applications where load bearing decking, hulls and walls are required.
The support structure also reduces tooling and fabrication costs. The support structure is easy to construct utilizing prefabricated components which are individually lightweight, yet structurally sound when utilized in combination. The modularity of the components enhances portability, facilitates pre-assembly and final positioning with light load equipment, and reduces the cost of shipping and handling the structural components. The support structure allows for easy construction of structures such as, but not limited to, bridges, marine decking applications and other construction and transportation applications.
The load bearing deck of the modular structural section also includes at least one sandwich panel including an upper surface, a lower surface and a core. The core includes a plurality of substantially hollow, elongated core members positioned between the upper surface and the lower surface. Each of the elongate core members includes a pair of side walls. The side walls can be formed and disposed in a variety of shapes angles with respect to the upper and lower walls. Each core member has side walls positioned generally adjacent to a side wall of an adjacent core member. The upper and lower surfaces of the sandwich panel are preferably an upper facesheet and lower facesheet formed of a polymer matrix composite material. In one embodiment, the upper and lower facesheets are formed of polymer matrix composite arranged in a hybrid of alternating layers including carbon and E-glass fibers in vinylester or polyester resin.
In one embodiment of the bridge described herein for a 30 foot span highway bridge, the individual components including the beams and the sandwich panels for the deck of the modular structural section each weigh less than 3600 pounds. Being constructed of a number of modular structural sections including components manufactured from polymer matrix composites, instead of concrete, steel and wood, the bridge has individual modular components which are fault tolerant in manufacture, as twisting and small warpage can be corrected at assembly. These properties of the bridge components decrease the cost of manufacture and assembly for the bridge. These components, including lightweight modular structural sections manufactured under controlled conditions, also allow for low cost assembly of a number of applications, such as marine structures, including the various applications described herein.
Another aspect of the present invention is a method of constructing a support structure such as highway bridge. The method comprises the following steps. First, a plurality of spaced-apart support members having a predetermined shape, for example a contoured shape, are provided. Next, a modular structural section is positioned on the plurality of spaced-apart support members. In one embodiment, the elongate support members of the modular structural section have a contoured shape which matably joins with and is supported on the contoured shape of support members. The modular structural section and the support members are then in various embodiment connected.
In one embodiment, the modular structural section is positioned by: first, positioning the beam having a contoured shape upon adjacent of the support members having a contoured shape for matably joining with and supporting the beam; then positioning the load bearing deck upon the beam, then connecting the at least one beam with the deck.
In another embodiment, a load bearing pad is first positioned on a flat cap portion of a support member. Then, the modular structural section is positioned on the load bearing pad with the flat floor of the beam positioned on the load bearing pad.
The methods of the present invention provide significantly reduced time, labor and cost as compared to conventional methods of bridge and support structure construction utilizing concrete, wood and metal structures.